# Compressible flow problem

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 March 5, 2014, 00:40 Compressible flow problem #1 Senior Member   Bharath kumar Join Date: Apr 2009 Posts: 169 Rep Power: 10 Sponsored Links Hi to all, I am simulating a compressible flow with Steam(Equilibirium) in CFX.My input BC's are, Inlet Total Pressure = 0.05768 atm & T = 308.82 K (mass flow =111.17 kg/s) Outlet Static Pressure = 0.05004 atm Reference Pressure = 0 atm Material: Steam Vapour (IAPWS table). I started with water ideal gas and it is converged.When switching to steam it is not able start the calculation. I tried different options and getting different warnings(Invalid number,Floating point, Over flow,High mach number,Table Clipping error and etc..) Could anybody help me to solve this problem. Thanks in Advance

 March 5, 2014, 05:24 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,737 Rep Power: 106 IAPWS are always hard to converge. You are using the ideal gas result as an initial condition? That will help a lot. Also (the standard stuff for numerical instability): Improve mesh quality, double precision numerics, smaller time steps, start with low order advection (Upwinding).

 March 11, 2014, 06:03 #3 Senior Member   Bharath kumar Join Date: Apr 2009 Posts: 169 Rep Power: 10 Thanks Glenn for your reply. 1) After so many trials i managed to converge 2 cases (Total 5 different Pressure BC cases & Same mesh).But other cases reporting high Mach number and solver is failing. 2) How i can deal this high mach number warning...

 March 11, 2014, 07:21 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,737 Rep Power: 106 As I said: Improve mesh quality, double precision numerics, smaller time steps, start with low order advection (Upwinding).

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